EP0131342A2 - Elektrophoretische Kamera - Google Patents

Elektrophoretische Kamera Download PDF

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Publication number
EP0131342A2
EP0131342A2 EP84200998A EP84200998A EP0131342A2 EP 0131342 A2 EP0131342 A2 EP 0131342A2 EP 84200998 A EP84200998 A EP 84200998A EP 84200998 A EP84200998 A EP 84200998A EP 0131342 A2 EP0131342 A2 EP 0131342A2
Authority
EP
European Patent Office
Prior art keywords
photoconductor
electrode
electrophoretic
disposed
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP84200998A
Other languages
English (en)
French (fr)
Other versions
EP0131342B1 (de
EP0131342A3 (en
Inventor
Ronald David Pinker
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Filing date
Publication date
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0131342A2 publication Critical patent/EP0131342A2/de
Publication of EP0131342A3 publication Critical patent/EP0131342A3/en
Application granted granted Critical
Publication of EP0131342B1 publication Critical patent/EP0131342B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
    • G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis

Definitions

  • the present invention is directed to an electrophoretic display device.
  • the present invention utilizes a light-sensitive photoconductor in an electrophoretic display for achieving memory effects with a light image.
  • Electrophoretic imaging displays involve an electrophoretic suspension sandwiched between two transparent electrodes, such as may be seen in U.S. patent 4,203,106 and the article by Murau et al in IEEE Trans. Elect. Devices, Vol. ED-26, No. 8, August 1979.
  • This suspension is comprised of charged pigment particles of one color suspended in a contrasting color, dyed solvent. Under an electric field, positive particles will migrate to a negative electrode or negative particles will migrate to a positive electrode. An image is then formed of contrasting colored pigment particles against a dyed background.
  • patterned indium oxide electrodes provide a numeric read-out, while a patterned grid structure provides an alpha-numeric display.
  • photoconductors sensitive to X-rays have been used in contact with this suspension for X-ray imaging.
  • a light-sensitive photoconductor is used in the present invention in contact with the electrophoretic suspension so that a light image is obtained by projecting a light image onto the photoconductor.
  • Such light images can be provided by various techniques including a slide projector focussing an image onto the photoconductor, a transparency focussed onto the photoconductor, a laser for writing images onto the photoconductor, and video systems for recording images from a CRT monitor.
  • the display of the present invention can be used for recording text, previewing slide film negatives, and constructing temporary security badges, for example.
  • Such displays can be portable, and have memories lasting at least from a few days to several weeks.
  • An ideal use for such a display would be to record time schedules of events from a television which could be maintained for a period of time for viewing.
  • the structure of the invention is easily transportable.
  • a convenient modification and use of the display of the present invention is in a camera.
  • the light-sensitive display is substituted for film and an image of the proposed picture can be formed without wasting film.
  • Film can then be substituted into the camera to obtain a hard copy.
  • An important result of the construction according to the present invention is that light images having good resolution (such as about 4 line pairs/mm or lp/mn) and good gray scale can be provided.
  • the invention seeks to improve to as many as 20 gray scales, and at least in the range of 10-20 gray scales. Exposure times can be relatively short, such as 10 to 40 mSec, with a light source of about 1-2 foot-Lamberts or ft.L. Images of people and places are easily discernable in such a structure, and the images can be stored or erased so that the device can be used again.
  • a first substrate 1 is provided with a conductive layer 2, such as indium oxide.
  • a photoconductor 3 is provided on the conductive layer 2, and this structure of substrate 1, electrode 2, and photoconductor 3 is spaced from another conductive surface 5 mounted on a second substrate 6.
  • the spacing is provided by a spacer 7 and an electrophoretic suspension 4 is provided in the space.
  • Epoxy 8 binds the various layers together.
  • cadmium sulfide has been found to be a useful light addressable photoconductor.
  • Cadmium sulfide provides very good images in a light addressable photoconductor.
  • Lead oxide is also a light sensitive photoconductor that is used although it is not as sensitive as CdS.
  • selenium provides a good light-sensitive photoconductor which also can be used in the structures of the present invention.
  • the principle criteria in selecting the light sensitive photoconductor is that it be inert in contact with the suspension medium. This rules out organic photoconductors.
  • a CdS-type photoconductor for example, is mixed with an epoxy binder and applied to the substrate 1 and conductive layer 2. Such application can be by coating or spraying. It has been found that CdS photoconductive layers to approximately 50-100 microns thickness is quite adequate. In all cases the light sensitive photoconductor has an area covering 3 by 3 inches to as large as 14 by 17 inches.
  • a polycrystalline binder layer of tetragonal lead oxide has been used. Such a material is settled from a slurry onto the substrate 1 and conductive layer 2 to give a uniform layer approximately 90 microns thick.
  • the substrate 1 and conductive layer 2 can be glass coated with indium oxide.
  • a mylar spacer 7 is used to provide a gap of 100 microns between the photoconductor layer 3 and the conductive layer 5 and substrate 6.
  • the device is sealed with epoxy 8, and after curing the epoxy, the electrophoretic suspension 4 is introduced into the device through pre- drilled holes in the structure 5, 6.
  • the electrode 5 may also be indium oxide while the substrate 6 is a viewing substrate such as glass. In this structure an observer 10 can view the suspension 4 by way of the light 9 shining through the device.
  • the electrophoretic suspension 4 involves four basic ingredients, i.e. pigments, solvent, stabiler, and dye. It has been found that the nature of this suspension is complex due to interaction of the various components. Consequently, any variation in one component will effect the function of the other materials.
  • the pigment acts to reflect incident light back to the viewer. Consequently, a pigment having a bright color with a high refractive index is required. Moreover, the pigment should be inert in the system and capable of being charged. Therefore, a low specific gravity organic pigment, such as diarylide yellow is employed. Diarylide yellow is satisfactory in meeting all the above requirements for a pigment without any alterations.
  • a further aspect of the suspension is that the solvent acts as a suspending medium for the pigment.
  • a solvent is chosen whose density is the same as the pigment in order to avoid settling of the pigment. Mixtures of solvents, such as tetrachloroethylene,xylene, can also be used in order to achieve density matching.
  • a suitable solvent would have a low refractive index, a low viscosity, and a high resistivity.
  • the dye utilized in the suspension provides the dark background. Thus, it is very important that the dye have a high absorption coefficient. Black and blue are the preferred colors. On the other hand, the dye should have a low conductivity so as not to interact with the pigment by way of absorption, as well as to be soluable in the solvent.
  • the Sudan family of dyes are among those that can be effect- tively used.
  • the suspension requires a stabilizer.
  • An example is 06A ⁇ 470 by Chevron.
  • stabilizers There are two types of stabilizers that can be used, namely those providing charging agents, and those providing dispersing agents. Charging agents impart a charge to the pigment particles in order to render it electrophorectically active. Dispersion agents prevent floculation of the particles in suspension such as by adsorption of long polymer chains. Some stabilizers may act as both charging agents and dispersing agents for stabilizing the pigment.
  • an erasure A.C. square-wave field is applied of about 400 volts. This electric field causes switching of the pigment particles between electrodes 2 and 5. Any previous latent images will be erased upon application of such field.
  • the photoconductor electrode 2 being positive by 400 V, for example, so that all of the pigment in the electrophoretic suspension, assuming a negative pigment charge, will be attached to the photoconductor.
  • the electrode 5 at the viewing side will appear black.
  • the light source 9 is pulsed for an appropriate amount of time, such as 20 mSec to 100 mSec.
  • the electric field is removed by shorting the electrodes 2 and 5.
  • the pigment particles at areas where the photoconductor was not exposed will then switched to the viewing electrode, but pigment particles will remain attached to the photoconductor where the photoconductor was illuminated by the light source 9.
  • the photoconductor When the photoconductor is biased to be positive , for example, negative pigment particles will be attracted to the photoconductor surface.
  • the illuminated photoconductor Upon making an exposure, the illuminated photoconductor undergoes an internal polarization involving the formation and separation of electron-hole pairs. The holes are swept to the photoconductor/ suspension interface.
  • the image is developed by removing the voltage and shorting the electrodes.
  • the removal of the external voltage ( ⁇ V) causes a simi1ar ⁇ V at the photoconductor surface resulting in a negative potential that repels the pigment to the electrode 5 at the viewing side of the device.
  • This electrophoretic imaging device of Figure 1 will produce a stored image that will remain for at least a few days without any applied voltage. In fact, the stored image will remain almost indefi- nately if undisturbed. It is portable can be easily operated, and is fast in operation requiring from around 100 mSec. to about 115 mSec. for development.
  • this device involves the storage of frames from a CRT.
  • the electrophoretic display device 20 having the above construction, would be placed adjacent to a CRT 21 and information on the CRT would be written into the display for temporary storage.
  • the use of a lens arrangement 23 can be used to project the image from the CRT 21 to the display device 20. This offers a quick and easy technique for storing information from a television, for example.
  • a large area liquid crystal 22 at the substrate 1 of the display device.
  • Such a large area liquid crystal would act as a shutter or light valve for the light.
  • Another possibility is to actively address the electrophoretic display device 30 of the present invention with a laser 31, as may be seen in Figure 3.
  • a laser 31 As may be seen in Figure 3.
  • information or graphics can be written onto the display with the laser 31 using a computer keyboard terminal 32.
  • the entire arrangement is controlled by the keyboard 32 and controlling computer circuitry 33 for the laser 31.
  • the device may be used in conjunction with a camera structure 41, such as illustrated in Figure 4.
  • the display 40 can be formed as separate element which is substituted in a camera in place of film.
  • a temporary image can be obtained through the camera 41 onto the electrophoretic display. This would be convenient in determining correct f-stop, shutter speed and other characteristics of the camera.
  • a film pack 42 could be exchanged with the electrophoretic display 40 to obtain a hard copy without unnecessary waste of film.
  • the image on the display can be stored for days without any additional voltages applied thereto.
  • the display 40 and the film pack 42 can be arranged to be removably interchanged or arranged to be changeably moved in permanent mountings in the camera structure 41. This would involve an arrangement for interchanging the display 40 and film pack 42 to be alternately placed in the camera for exposure to an object.
  • a photoconductor is not as sensitive as film, an effective image can be obtained on the display for checking the image of the object before exposure to the film 42.
  • This type of structure makes available the concept of reusable film. For example, such structures can be used in security badges.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
EP84200998A 1983-07-11 1984-07-10 Elektrophoretische Kamera Expired - Lifetime EP0131342B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US51251783A 1983-07-11 1983-07-11
US512517 1983-07-11

Publications (3)

Publication Number Publication Date
EP0131342A2 true EP0131342A2 (de) 1985-01-16
EP0131342A3 EP0131342A3 (en) 1986-08-13
EP0131342B1 EP0131342B1 (de) 1991-04-24

Family

ID=24039433

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84200998A Expired - Lifetime EP0131342B1 (de) 1983-07-11 1984-07-10 Elektrophoretische Kamera

Country Status (3)

Country Link
EP (1) EP0131342B1 (de)
JP (1) JPS6052828A (de)
DE (1) DE3484487D1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5255327A (en) * 1986-07-02 1993-10-19 Ken Hayashibara Vibrostimulative device
CA2012034A1 (en) * 1989-03-20 1990-09-20 Takahiko Ono Vibration generator using rotary bodies having unbalanced weights, and vibratory stimulating apparatus using same vibration generator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2046348A5 (de) * 1969-04-23 1971-03-05 Matsushita Electric Ind Co Ltd
DE2216766A1 (de) * 1971-04-29 1972-11-09 Vockenhuber, Karl, Ing.; Hauser, Raimund, Dr.; Wien Sucher
DE2442257A1 (de) * 1973-09-04 1975-03-06 Itek Corp Optisch-adressierbare anzeigevorrichtung

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5275294A (en) * 1975-12-19 1977-06-24 Matsushita Electric Ind Co Ltd Display device
JPS55113079A (en) * 1979-02-23 1980-09-01 Ricoh Co Ltd Image forming method by photoelectrophoresis

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2046348A5 (de) * 1969-04-23 1971-03-05 Matsushita Electric Ind Co Ltd
DE2216766A1 (de) * 1971-04-29 1972-11-09 Vockenhuber, Karl, Ing.; Hauser, Raimund, Dr.; Wien Sucher
DE2442257A1 (de) * 1973-09-04 1975-03-06 Itek Corp Optisch-adressierbare anzeigevorrichtung

Also Published As

Publication number Publication date
EP0131342B1 (de) 1991-04-24
JPS6052828A (ja) 1985-03-26
DE3484487D1 (de) 1991-05-29
EP0131342A3 (en) 1986-08-13

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